Known rear seats provided in the rear of a vehicle compartment of, for example, a wagon type vehicle or a recreation vehicle (RV) are configured to be folded and stowed when the rear seats are not in use in order to expand the cargo space. For example, according to a known seat apparatus for a vehicle described in JP7-22355Y, an outer slide rail is mounted to a wheel house panel at a side wall of a vehicle body via a hinge mechanism, and a rear seat (seat cushion) is flipped up (folded) to be in a storage position at a wall portion. According to the construction described in JP7-22355Y, because the rear seat (seat cushion) is flipped up via the hinge mechanism to be in a storage position, a large degree of force is required to raise the seat to be in the storage position, thus causing difficulties for stowing the seat.
In order to solve the foregoing drawback, another known seat apparatus is disclosed in JP2005-96633A, which includes a spring means (assist spring) biasing the seat cushion in a direction for flipping the seat cushion up when stowing the seat cushion.
According to the seat apparatus described in JP2005-96633A, the force required for flipping the seat cushion up is reduced because of the biasing force of the spring when stowing the seat cushion at the wall portion of the vehicle compartment from a state where the seat is ready to be used.
The foregoing known seat apparatuses for the vehicle are structured to receive a load being in upward and downward directions from an upper rail by a lower rail via a bearing at a slide rail. However, with the construction of the seat apparatus for the vehicle including the assist spring, the hinge mechanism is rotated in a direction against the biasing force of the spring means, and thus is retained while storing the large degree of spring force biased by the spring means. In consequence, the lower rail fixed to the vehicle body is assumed to receive the load not just in the upward and downward directions but in a lateral direction and/or in a transverse direction, which results in a deformation of the lower rail and the bearing configured to receive the force primarily in the upward and downward direction, and thus causing a faulty operation. Although increasing a plate thickness of the lower rail and changing the material of the lower rail to a material with high rigidity are considered in order to prevent the deformation of the lower rail and the bearing as foregoing, those devices increase the weight and a manufacturing cost of the lower rail.
A need thus exists for a seat apparatus for a vehicle which is not susceptible to the drawback mentioned above.